A conventional liquid crystal display panel mainly includes a pair of glass substrates, a liquid crystal layer provided between the glass substrates, electrodes provided on the glass substrates, and polarizing plates attached to the respective glass substrates. On such a liquid crystal display panel, an image is recognized by contrasts which appear on a screen by light that has been emitted by a backlight and has then passed through the polarizing plates and the liquid crystal layer. According to the configuration, most of the light emitted by the backlight is lost by being absorbed and reflected before reaching a display screen, and this causes a decrease in light use efficiency. In particular, loss of light due to the polarizing plates significantly influences the decrease in light use efficiency.
Patent Literature 1 discloses an optical device (i) which includes a pair of electrodes, a polar solvent and a nonpolar solvent, and flakes each of which has a hydrophilic layer and a hydrophobic layer and (ii) in which a longitudinal orientation and a transverse orientation of the flakes are switched by changing whether or not to apply a voltage. Specifically, in a case where no voltage is applied to an electrode 52, flakes each of which has a hydrophilic layer 41 and a hydrophobic layer 42 are aligned in parallel with a substrate 51 (i.e., the transverse orientation) at an interface between a polar solvent 31 and a nonpolar solvent 32 so as to reflect light, etc. (see (a) of FIG. 20). On the other hand, in a case where a voltage is applied to the electrode 52, the flakes are aligned perpendicular to the substrate 51 (i.e., the longitudinal orientation) so as to allow light to pass through (see (b) of FIG. 20). According to the configuration, it is possible to omit polarizing plates unlike the liquid crystal display panel, and this makes it possible to increase light use efficiency.